Speaking about audio data, for example, data of 2 channels, namely, L and R channels, is predominant. In recent years, however, audio data of 3, 4 or more channels has been used widely.
In order to keep up with the popularization of such multi-channel audio data, the transmission format of the audio data is adapted to a variety of channel counts.
A detailed structure of transmitted data will be described later. Briefly speaking, however, in transmission of audio data by adoption of an SACD (Super Audio CD) technique conforming to IEEE-1394 specifications, for example, a transmitted-data stream is formed to include a sequence of units known as blocks each containing audio data. To be more specific, each block contains audio data of all channels.
FIGS. 10A to 10C are each a diagram showing the structure of a block. In the case of 2-channel audio data, a block consists of 4 quadlets q1 to q4 each having a size of 32 bits as shown in FIG. 10A. The second quadlet q2 is allocated to data of the L channel, which is used as the first channel or channel 1. On the other hand, the third quadlet q3 is allocated to data of the R channel, which is used as the second channel or channel 2.
It is to be noted that ‘D1’, ‘00’, ‘50’, ‘51’ and ‘CF’ shown in FIGS. 10A to 10C are each information called a label or a sub-label, which will be explained later in a description of an embodiment.
In the case of 5-channel audio data, a block consists of 6 quadlets q1 to q6 as shown in FIG. 10B. The second to sixth quadlets q2 to q6 are allocated to the first to fifth channels or channels 1 to 5 respectively. The first channel or channel 1 is the L channel, the second channel or channel 2 is the R channel, the third channel or channel 3 is the C (center) channel, the fourth channel or channel 4 is the Ls (rear left) channel and the fifth channel or channel 5 is the Rs (rear right) channel.
In the case of 6-channel audio data, a block consists of 8 quadlets q1 to q8 as shown in FIG. 10C. The second to seventh quadlets q2 to q7 are allocated to the first to sixth channels or channels 1 to 6 respectively. The first channel or channel 1 is the L channel, the second channel or channel 2 is the R channel, the third channel or channel 3 is the C (center) channel, the fourth channel or channel 4 is the LFE (Low Frequency Enhancement) channel, the fifth channel or channel 5 is the Ls (rear left) channel and the sixth channel or channel 6 is the Rs (rear right) channel.
A transmission block is defined for 2, 5 or 6 channels for example as described above so as to allow 2-channel, 5-channel or 6-channel audio data respectively to be transmitted.
In consequence, however, definition of transmission block for a specific channel count necessitates that the structure of a block be newly defined for transmission of audio data having a different channel count so to speak.
For example, a block needs to be newly defined for transmission of audio data having a channel count of 3, 4 or 7.
It is to be noted that the definition of a new block itself is possible from the technical point of view. In the definition of a new block, the number of quadlets composing a block needs to be merely determined properly and the quadlets need to be merely allocated to channel data appropriately.
However, data with a new block structure is transmitted with a newly prescribed transmission format, which is unknown to the reception apparatus previously developed and already shipped to the field in general.
Thus, there is raised a problem that the audio data cannot be received and processed correctly.